This application relates to detecting the presence of a workpiece in a handling environment, and more particularly to detecting the presence of a semiconductor wafer in a vacuum wafer handling system.
While numerous techniques are known for detecting the presence of objects, such as optical beam breaking, radar, sonar, and so forth, many of these techniques are not generally suitable for use in vacuum because the hardware cannot be deployed in vacuum or the hardware requires electrical, optical or other leads for which through-holes in a vacuum chamber must be provided. For high-vacuum applications such as semiconductor fabrication, there remains a need for improved techniques to detect the presence of a semiconductor wafer or the like within a vacuum chamber.